The current teaching in the art relies heavily on user skill and dexterity to determine the size (overall length) of a bullet. Common bullet comparators rely upon the user's ability to juggle the bullet into place to hopefully find a datum line from which to measure. This datum line, however, is a constructed line that relies on a visual queue based on a single ring-contact line, or datum-line, established by a fixture holding the bullet around its circumference and a single touch-point on the bullet's base, where the measuring instrument contact's the bullet. However, this approach causes considerable variability because repeatable and proper alignment of the bullet by the ring-contact fixture is imprecise.
The current art uses a dial caliper in conjunction with a ring-contact fixture. The bullet is placed in the ring-contact fixture; however, it is very easy to misalign the bullet in the fixture. To overcome this, and to establish the needed datum line, the user typically juxtaposes the bullet so that the calipers function more akin to a “C”-clamp, with the bullet precariously balanced between the caliper jaws. Then, the user pushes harder and harder to square the bullet in the ring-contact fixture using one caliper jaw on the base of the bullet and the other jaw pushing on the far end of the ring-contact fixture. And the, the user reads the measurement on the dial caliper.
The ring-contact fixture of the existing art is typically a hexagonal shaped fixture, similar in appearance to a “hex nut” with a uniquely dimensioned bore hole on each face. A common problem with this fixture is that a bullet can be off-center in the borehole, thus making repeatable measurements on the same bullet difficult.
Thus, there is a need for a bullet comparator that improves repeatability and accuracy of measurements. Such an improved comparator should utilize existing measurement instruments, such as a dial indicator, for example. Further, such an improved comparator should reduce or eliminate variability from off-center placement of the bullet in the fixture. Such an improved comparator should be reliable, repeatable, and easy-to-use.